I don't know if you've seen the stats for a Dragon in Burning Wheel, but it's extremely likely that no player ever will get a "low risk shot" at a dragon. However, I see your point. And, like Thor said, this just isn't an issue in play. Tests in scenes are fraught with risk. Players rarely have a chance to fuck around and live to tell the tale. And when they do? It's generally pretty funny.

It should be noted that the GM does have a say in what counts and what doesn't count towards advancement. Advancement's a shared thing between the players and the GM, after all, and it's ok to negotiate.

The most important concept to remember is that if the character's action isn't going to effect the story or there's no conflict involved, then there's no reason to roll those dice and no opportunity to mark a test earned towards advancement. BW GM's should always keep this in the forefront of their minds.

So, if that character was taking a pot shot at the dragon, he's going to throw away his chance of killing it before it kills him. But he's got to know that the dragon is going to kill him.

Honestly, in play, Burning Wheel characters don't tend to advance much beyond exponent 5 or 6 in their skills. The difficulty in obtaining Difficult and Challenging tests just gets too high. Instead, Burning Wheel characters tend to naturally broaden and extend outward with new, interesting skills as they are played.

just to add to this, Liam the Ranger from my defunct Miranna campaign began game with exp 6 archery. He ended on grey 8. To get that he had to perform running shots at extreme range towards eye-slits in helmets. And he got it. Capped his health at exp 4 in the processe, covered his body in scars and got him stabbed with a Morgul Dagger.

Like Thor says, you make a choice as a player.

Now I ha a guy who made a powerplay stunt. B6 power and the mr. Lee trait. And a beefed up Axe skill. Unfortunatly he forgot his Reflexes, a measly B3. Now when facing three Grey Trolls (orc equivalants), he whacked one. Out of actions he was quickly badly battered.Repeat.Repeat.